None of the Danes here have given any convincing answer on why they support the higher taxation on car registrations.
I am not sure what you mean by "external impact" here. You should clarify that first before I can answer your question. Also I hope you will forgive me for not reading your previous posts on other threads!
I get that you are in favour of high taxation. I am not against taxation either. But the question is how much higher is acceptable? 200% is acceptable for you? 300%? where do you put the upper limit? How do you measure the cost of driving cars on the society and environment? was 180% by the Danish government justified in this regard? What was the rationale behind that? I haven't gotten answer to this question from any Danes here or in Danish news papers or in person after talking to many Danes while working in Denmark for 8 months.
May be it is the whole Scandinavian model to blame. Therefore, I am giving you the example of Germany where taxes on cars are significantly low but at the same time salaries (at least in the tech sector) are comparable to Scandinavia, education is free, healthcare is affordable and cost of living is one of the best in the western world.
1. I would expect a state of the art public transport in the whole country. The rail system connecting different cities in Denmark is pretty dated and slow. Even using diesel engines in some parts. Now I would expect some part of that 180% tax to be invested here. But the fact is people are often forced to drive with car due to poor public transport connectivity in many places.
2. Even electric cars are not exempt from these high taxes anymore. This eliminates the benefit of the doubt that this was for the good of the environment.
3. The high tax for cars has historical roots. Many in Denmark believe it is no longer necessary today to fund the welfare state. https://www.thelocal.dk/20151120/whats-the-deal-with-denmark...
4. These high taxes are also defeating the purpose of keeping the environment clean by creating a huge market for used really old cars which are often the worst polluters. https://mereconomics.com/2016/02/09/on-the-efficiency-of-dan...
5. Opinion: It all boils down to having free health care, free education, really good welfare system and not being able to afford a car. Other European countries like Germany seem to have worked out a model which can make all of them affordable to most people.
I can go on but got bored.